1. Field of the Invention
The present invention relates generally to methods for recording images and apparatuses for recording images such as copying machine, facsimile and printer, and more particularly, to a method and an apparatus for recording images by intermittently allowing colorant particles to be ejected on a recording medium, thereby selectively applying on or permeating the particles into the medium to form images thereon.
2. Description of the Background Art
A conventional image recording apparatus has been proposed, by which colorant is evaporated, then ionized, and ejected intermittently based on an electrical signal corresponding to image data to be recorded, whereby the colorant is applied on or permeated into a recording medium to provide images. Such an image recording apparatus is for example disclosed by Japanese Patent Laying-Open No. 8-300803. The image recording apparatus will be now described.
FIG. 8 is a view for use in illustration of an example of a conventional image recording apparatus. In FIG. 8, the image recording apparatus includes a printing head 1. Printing head 1 is formed by integrating a heating device 10 to heat and evaporate colorant, a charging device 30 to charge the evaporated colorant, and an ejecting device 50 to intermittently eject the charged colorant based on an electrical signal corresponding to image data to be recorded.
Heating device 10 includes an electrical heater 10B. Charging device 30 includes an ionization electrode portion 30A having a needle shape for example, and a counter electrode portion 30B having a plate shape. In ejecting device 50, a back plate electrode portion 50C is provided at the back of a recording medium RM in order that the charged colorant through an ejecting outlet 90 onto recording medium RM for ejection with electrostatic force, an intermediate electrode portion 50A (50A1, 50A2, 50A3) is provided around ejecting outlet 90, and an intermediate electrode driving control portion 50E is also provided. Intermediate electrode portion 50A (50A1, 50A2, 50A3) has a so-called shutter function to physically or electrically control the ejection of the colorant. Intermediate electrode driving portion 50E outputs a driving signal corresponding to an input electrical signal corresponding to image data and controls intermediate electrode portion 50A (50A1, 50A2, 50A3) in a shutter manner. An insulating plate 50D is provided around intermediate electrode portion 50A (50A1, 50A2, 50A3).
In printing head 1, powder ink IP is previously stored. Heating device 10 to heat ink IP is provided at the lower half of printing head 1. At the upper half of printing head 1, a wire electrode from 50 xcexcm to 80 xcexcm is provided as charging device 30 to charge heated and evaporated ink IPG. At the upper part of printing head 1, an ejecting outlet 90 of xcfx86300 xcexcm to allow evaporated ink IPG to be ejected therethrough is provided, and intermediate electrode portion 50A (50A1, 50A2, 50A3) having an inner diameter of xcfx86300 xcexcm is provided to surround ejecting outlet 90.
The operations of the image recording apparatus shown in FIG. 8 will be now described. During printing, ink IP is heated to 200xc2x0C. and evaporated. When colored inks are used, the colorant may include as a base, anthoraisothiazole, quinophthalone, pyazolonazo, pyiidone azo, styryl or the like for yellow, anthraquinone, dicyanoimidazole, thiadiazoleazo, tricyanovinyl, or the like for magenta, and azo, anthraquinone, naphthoquinone, indoaniline, or the like for cyan. Evaporated ink IPG is ionized by applying a voltage at +5 kV to charging device 30. Ionized evaporated ink IPG is controlled to be ejected on recording medium RM in response to application of a prescribed voltage to back plate electrode portion 50C and intermediate electrode portion 50A (50A1, 50A2, 50A3).
The image recording apparatus shown in FIG. 8 however suffers from the following disadvantage. When ink is ionized by a strong electric field in the vicinity of ionization electrode portion 30A, the ionization efficiency is low, i.e., the efficiency of transporting of evaporated ink IPG into a possible ionization area and the efficiency of ionization of evaporated ink IPG thus transported in total are low, therefore the ratio of effective evaporated ink which can be controlled for ejection is small, and the recording speed is low. If an electric field to ionize evaporated ink IPG is generated, air in the vicinity of ionization electrode portion 30A is also ionized. Therefore, the ions act as a driving force to cause a flow of ionized air, evaporated ink IPG present in the area where the ionized air flows is brought by the flow and sticks to counter electrode portion 30B. As a result, the percentage of evaporated ink IPG which can be used for recording is low.
It is an object of the present invention to provide a method and an apparatus for recording images, which allows for increase in the charging efficiency of colorant particles, the charge amount, the use efficiency and the recording speed and permits good picture qualities to be provided.
In order to achieve this object, an image recording method according to the present invention includes the following characteristics. More specifically, the method includes the steps of generating colorant particles from ink colorant, charging the generated colorant particles, and intermittently ejecting the charged colorant particles onto a recording medium by electrostatic force based on an electrical signal corresponding to prescribed image data.
The colorant particles are transported sequentially from the generating step to the charging step and to the ejecting step.
The generating step may further include the steps of heating and evaporating ink colorant, cooling, solidifying and agglomerating the evaporated ink colorant, thereby granulating the colorant into colorant particles.
In the image recording method as described above, the colorant particles generated in the generating step are transported sequentially from the generating step to the charging step and the ejection step, and therefore the colorant particles may securely gone through each step, so that the use efficiency of the colorant in image recording may be improved and the charge amount may become even.
Since the colorant particles are transported while controlling the flow of air including the colorant particles in the above image recording method, the colorant particles generated in the generating step are transported surely to the following steps in the flow of air. The airflow is controlled, and therefore the colorant particles will not be attached in an undesired location in the flow path or the amount of ejection in the ejection step will not be uneven. Thus, the colorant particle density may be improved to increase the recording speed as a result.
In order to achieve the above-described object of the present invention, an image recording apparatus according to the present invention records prescribed images on a recording medium using ink colorant has the following characteristics. More specifically, the apparatus includes a generating portion which generates colorant particles from ink colorant, a charging portion which charges the generated colorant particles, an ejecting portion which intermittently ejects the charged colorant particles onto the recording medium by electrostatic force based on an electrical signal corresponding to prescribed image data, and a transport portion which sequentially transports the colorant particles from the generating portion to the charging portion and the ejecting portion.
Therefore, the generated colorant particles are surely passed through each portion, the use efficiency of the colorant is improved and the charge amount may become even.
In the above image recording apparatus, the generating portion may include a heating portion for heating and evaporating colorant, and a granulating portion for cooling, solidifying and agglomerating the colorant evaporated by the heating portion, thereby granulating the colorant into colorant particles.
The granulating portion may include a particle size control portion which controls the particle size in granulating the ink colorant evaporated by the heating portion.
Therefore, the particle size of the ink colorant is controlled at a size suitable for recording by the particle size control portion, and good quality images result.
The transport portion as described above may include an airflow generating portion to generate an airflow for sequentially transporting the colorant particles from the generating portion to the charging portion and the ejecting portion, and a flow control portion to control the generated airflow.
Therefore, generated colorant particles are surely transported to each portion by the transport portion. Furthermore, the flow control portion may control the airflow, which prevents the colorant particles from being attached in an undesired location in the flow path, and the ejection amount from becoming uneven, so that the recording speed may be improved.
The charging portion as described above has its lengthwise direction corresponding to the transport direction of the colorant particles, and may include corona discharge means which is arranged in axial symmetry in a cross sectional direction corresponding to the transport direction.
Thus, the air ions generated by corona discharge at the charging portion may move along the line of electric force and impinge the colorant particles being transported to charge the colorant particles, and therefore almost the entire colorant may be charged, so that the charging efficiency may be improved. As a result, the ejection speed and the recording speed increase, and good quality recorded images may be stably provided.
A flow of ionized air is generated at the charging portion by corona discharge, but the colorant particles are transported in an airflow by the transport portion, and therefore the amount of colorant particles drawn to the ionized airflow at the charging portion attached to an undesired part of the charging portion may be reduced.
Since at the charging portion the ionized air impinges upon all the colorant particles transported by corona discharge, few uncharged particles are generated, and variations in the charge amount may be restrained as well. Furthermore, the lengthwise direction of the charging portion corresponds to the transport direction of colorant particles, and therefore a long time period may be secured for charging the colorant particles, which may increase the charge amount.
In the image recording apparatus as described above, a circulating flow path structure to sequentially circulate the colorant particles through the generating portion, charging portion and ejecting portion may be employed.
Thus, the colorant particles circulate each portion in the image recording apparatus, and colorant particles not used for recording may be recycled. These unused colorant particles are once again transported to the charging portion, has its charge amount increased and is then used for recording, which improves the use efficiency of the colorant particles. In addition, since the charge amount for colorant particles increases, the ejection speed increases, and an increased recording speed results.
The above-described generating portion may be an ultrasonic vibrating portion which vibrates ink colorant by an ultrasonic to generate colorant particles.
The above-described transport portion may include a speed control portion to limit the transport speed of colorant particles. Thus, the transport speed of colorant particles may be controlled such that images may be appropriately recorded.